1. Field of the Invention
The present invention relates to a system to incinerate con-taminants released in the regeneration or reconcentration process of glycol dehydration of natural gas.
2. Prior Art
Natural gas processing includes removal of contaminants from the natural gas in order to produce a transportable natural gas product. One of the major contaminants removed during processing is water vapor in the gaseous state and water in condensed form. Other contaminants present in smaller quantities are heavy hydrocarbons, solid matters such as sand, and acid gasses.
There are two methods for removing water from natural gas. Although dry desiccants are utilized in some applications, liquid absorbent systems are most frequently used.
Most large volume dehydration units are of the glycol type. Glycol is advantageous because it has a relatively high boiling point, is thermally stable and does not oxidize in normal use. The media used is glycol of one of three kinds: ethylene, diethylene, or triethylene, with triethylene or "teg" the most frequently used. Water in natural gas is absorbed by contact with teg.
A typical dehydration facility normally consists of an inlet gas scrubber and separator where liquid accumulations are removed. The gas is then directed to a gas contactor where the triethylene glycol comes into contact with the gas, a majority of the water vapor being absorbed by the glycol. The dehydrated gas leaves the contactor tower where it is directed to be transported for use. The wet glycol is directed from the contactor tower through a series of skimmers and filters and then to a reconcentrator or reboiler column.
In the reboiler column, the water saturated glycol is heated to a temperature of between 380.degree. to 400.degree. Fahrenheit to boil off the water. At the same time, it is advisable to maintain the reboiler at the lowest possible pressure so that the water solubility of glycol is not increased.
The vaporized water, along with the contaminants not removed with the skimming and filtration process, are typically vented to the atmosphere. Venting these contaminants to the atmosphere is becoming an increasing environmental problem. These odorous vapors emitted from the reboiler create uncomfortable living conditions and health concerns for local residents and workers. It is to this problem that the present invention is directed.
A patentability search was conducted by the applicant on the present invention and the following U.S. patents represent the results of the search:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 4,237,620 Black December 9, 1980 4,494,967 Barth January 22, 1985 4,676,806 Dean et al. June 30, 1987 3,395,512 Finney et al. August 6, 1968 4,280,867 Hodgson July 28, 1981 4,182,659 Anwar et al. January 8, 1980 4,162,145 Alleman July 24, 1979 2,725,337 Laurence et al. November 29, 1955 4,003,722 Holter January 18, 1977 ______________________________________
Hodgson (U.S. Pat. No. 4,280,867) discloses a reboiler used to heat wet glycol and water vapor is discharged. The dehydrated glycol then flows through a stripping column where glycol comes into contact with dry flue gas generated by a catalytic burner.
Anwar et al (U.S. Pat. No. 4,182,659) provides a system where wet glycol is initially drawn off into an expansion chamber where part of the hydrocarbon gases absorb, are drawn off and may be re-used as heating gas. The glycol is then heated to remove the majority of the water which is vented to the atmosphere. Finally, the glycol is heated at sub-atmospheric pressure (vacuum) to further purify it.
Holter (U.S. Pat. No. 4,003,722) discloses a system where gas may be purified by cleansing fluid. The cleansing fluid may be admitted into a flow circuit into an evaporator causing the impurities to be evaporated by heating. The impurities liberated in the evaporator are conveyed to a burner or combustion chamber and combusted.
Accordingly, it is a principal object and purpose of the present invention to provide a system for control and disposal of contaminants released in the glycol regeneration process without venting such contaminants to the atmosphere.
It is a further object and purpose of the present invention to provide a system for control and disposal of contaminants released in the glycol regeneration process wherein the contaminants may be incinerated without production of odors or visible emissions.
It is a further object and purpose of the present invention to provide a system for control and disposal of contaminants released in the glycol regeneration process which will not add undue back pressure to the reboiler.